Method for manufacturing interposer

ABSTRACT

A method for manufacturing an interposer equipped with a plurality of through-hole electrodes comprises a laser light converging step of converging a laser light at a sheet-like object to be processed made of silicon so as to form a modified region in the object; an etching step of anisotropically etching the object after the laser light converging step so as to advance etching selectively along the modified region and form a plurality of through holes in the object, each through hole being tilted with respect to a thickness direction of the object and having a rectangular cross section; an insulating film forming step of forming an insulating film on an inner wall of each through hole after the etching step; and a through-hole electrode forming step of inserting a conductor into the through holes so as to form the through-hole electrodes after the insulating film forming step; wherein the plurality of through holes are arranged such that the through holes aligning in the tilted direction are staggered in a direction perpendicular to the tilted direction as seen from a main face of the object.

TECHNICAL FIELD

The present invention relates to a method for manufacturing aninterposer.

BACKGROUND ART

Known as an example of conventional methods for manufacturing aninterposer is one disclosed in Patent Literature 1. First, in thismethod for manufacturing an interposer, a sheet-like object to beprocessed is irradiated with a laser light, so as to form a precursoryhole in the object. Subsequently, the object 1 is etched, so as toenlarge the precursory hole, thereby forming a through hole. Then, aconductor is inserted into the through hole, so as to form athrough-hole electrode, thereby manufacturing an interposer.

CITATION LIST Patent Literature

Patent Literature 1: Japanese Patent Application Laid-Open No.2006-352171

SUMMARY OF INVENTION Technical Problem

Recently, as demands for small-sized electronic devices with highquality have been increasing, it has strongly been required for theabove-mentioned prior art to manufacture interposers which can be madesmaller while securing high reliability.

It is therefore an object of the present invention to provide a methodfor manufacturing an interposer which can be made smaller while securinghigh reliability.

Solution to Problem

For achieving the above-mentioned object, the method for manufacturingan interposer in accordance with one aspect of the present invention isa method for manufacturing an interposer equipped with a plurality ofthrough-hole electrodes, the method comprising a laser light convergingstep of converging a laser light at a sheet-like object to bi processedmade of silicon so as to form a modified region in the object; anetching step of anisotropically etching the object after the laser lightconverging step so as to advance etching selectively along the modifiedregion and form a plurality of through holes in the object, each throughhole being tilted with respect to a thickness direction of the objectand having a rectangular cross section; an insulating film forming stepof forming an insulating film on an inner wall of each through holeafter the etching step; and a through-hole electrode forming step ofinserting a conductor into the through holes so as to form thethrough-hole electrodes after the insulating film forming step; whereinthe plurality of through holes are arranged such that the through holesaligning in the tilted direction are staggered in a directionperpendicular to the tilted direction as seen from a main face of theobject.

In this method for manufacturing an interposer, the through holesaligning in the tilted direction are arranged such as to be staggered ina direction perpendicular to the tilted direction. Therefore, aplurality of through holes and, as a consequence, a plurality of throughholes can be arranged densely in the object, whereby the resultinginterposer can be made smaller. Here, since through holes having arectangular cross section are formed, projections which inhibitinsulating films from growing are harder to form on the inner faces ofthe through holes. Therefore, the insulating film forming step can formuniform insulating films, thereby suppressing defects in the insulatingfilms and securing high reliability.

The laser light converging step may form a first modified region as themodified region in a part corresponding to the through hole in theobject and a second modified region as the modified region joining withthe first modified region in a part to be removed upon thinning by theanisotropic etching, and the etching step may advance the etchingselectively along the second modified region and then along the firstmodified region while thinning the object to a target thickness andcomplete forming the through holes when the object is at the targetthickness. In this case, the etching for the first modified region doesnot begin to progress when the object is at the target thickness, but isinduced to start to advance by the second modified region formed in thepart to be removed by thinning when thinning the object to the targetthickness by etching, and the forming of the through holes completeswhen the object is thinned to the target thickness. This can inhibit theetching from increasing the aperture size of the through holes on theopening sides, whereby the through holes can be formed accurately.

The second modified region may extend parallel to the thicknessdirection of the object. This makes it easier to specify and manage theconverging point of the laser light when forming the second modifiedregion, whereby the laser processing can be facilitated.

The object may have a main face which is a (100) plane. This canfavorably form through holes tilted in the thickness direction in theobject.

The laser light converging step may comprise a first step of repeatedlyperforming a step of irradiating the object with the laser light whilerelatively moving a converging point of the laser light along a firstdirection orthogonal to a laser light irradiation direction, whilechanging a depth position of the converging point in the irradiationdirection and a second step of repeatedly performing the first stepwhile changing a position of the converging point in a second directionorthogonal to the irradiation direction and first direction. This canshorten the takt time of the laser light converging step.

Advantageous Effects of Invention

The present invention can provide a method for manufacturing aninterposer which can be made smaller while securing high reliability.

BRIEF DESCRIPTION OF DRAWINGS

[FIG. 1] is a schematic structural diagram of a laser processing deviceused for forming a modified region;

[FIG. 2] is a plan view of a object to be processed in which themodified region is to be formed;

[FIG. 3] is a sectional view of the object taken along the line III-IIIof FIG. 2;

[FIG. 4] is a plan view of the object after laser processing;

[FIG. 5] is a sectional view of the object taken along the line V-V ofFIG. 4;

[FIG. 6] is a sectional view of the object taken along the line VI-VI ofFIG. 4;

[FIG. 7] is a schematic sectional view illustrating an interposermanufactured by an embodiment;

[FIG. 8] is a schematic perspective view of the interposer of FIG. 7;

[FIG. 9](a) is a flow diagram illustrating the embodiment, while (b) isa flow diagram illustrating a sequel to FIG. 9( a);

[FIG. 10](a) is a flow diagram illustrating a sequel to FIG. 9( b),while (b) is a flow diagram illustrating a sequel to FIG. 10( a);

[FIG. 11](a) is a flow diagram illustrating a sequel to FIG. 10( b),while (b) is a flow diagram illustrating a sequel to FIG. 11( a);

[FIG. 12](a) is a flow diagram illustrating a sequel to FIG. 11( b), (b)is a flow diagram illustrating a sequel to FIG. 12( a), and (c) is aflow diagram illustrating a sequel to FIG. 12( b);

[FIG. 13] is a sectional view corresponding to a cross section takenalong the line XIII-XIII of FIG. 12( c) and illustrating a through holeformed by the embodiment;

[FIG. 14](a) is an enlarged sectional view illustrating a part of theobject after forming modified regions therein, while (b) is an enlargedsectional view illustrating a part of the object after forming throughholes therein;

[FIG. 15](a) is a sectional view corresponding to FIG. 13 andillustrating another example of through holes, while (b) is a sectionalview corresponding to FIG. 13 and illustrating still another example ofthrough holes; and

[FIG. 16] is a schematic sectional view illustrating an interposer of avariation.

DESCRIPTION OF EMBODIMENTS

In the following, preferred embodiments of the present invention will beexplained in detail with reference to the drawings. In the explanationof the drawings, the same or equivalent constituents will be referred towith the same signs while omitting their overlapping descriptions.

The interposer manufacturing method in accordance with an embodimentconverges a laser light into a object to be processed, so as to form amodified region. Therefore, the forming of the modified region willfirstly be explained in the following with reference to FIGS. 1 to 6.

As illustrated in FIG. 1, a laser processing device 100 comprises alaser light source 101 which causes a laser light L to oscillate in apulsating manner, a dichroic mirror 103 arranged such as to change thedirection of the optical axis (optical path) of the laser light L by90°, and a condenser lens 105 for converging the laser light L. Thelaser processing device 100 also comprises a support table 107 forsupporting a object to be processed 1 irradiated with the laser light Lconverged by the condenser lens 105, a stage 111 for moving the supporttable 107, a laser light source controller 102 for controlling the laserlight source 101 in order to regulate the output, pulse width, and thelike of the laser light L, and a stage controller 115 for controllingthe movement of the stage 111.

In the laser processing device 100, the laser light L emitted from thelaser light source 101 changes the direction of its optical axis by 90°with the dichroic mirror 103 and then is converged by the condenser lens105 into the object 1 mounted on the support table 107. At the sametime, the stage 111 is shifted, so that the object 1 moves relative tothe laser light L along a part to form a modified region 5. This forms amodified region in the object 1 along the part 5.

As illustrated in FIG. 2, the part 5 is set in the object 1, for which asemiconductor material, a piezoelectric material, or the like is used.Here, the part 5 is a virtual line extending straight. When forming amodified region in the object 1, the laser light L is relatively movedalong the part 5 (i.e., in the direction of arrow A in FIG. 2) whilelocating a converging point P within the object 1 as illustrated in FIG.3. This forms a modified region 7 within the object 1 along the part 5as illustrated in FIGS. 4 to 6, whereby the modified region 7 becomes aremoving region 8 to be removed by etching which will be explainedlater.

The converging point P is a position at which the laser light L isconverged. The part 5 may be curved instead of being straight, shapedinto a three-dimensional form combining them, or specified in terms ofcoordinates. The modified region 7 may be formed either continuously orintermittently. The modified region 7 may be formed like lines or dots.It will be sufficient if the modified region 7 is formed at least withinthe object 1. There are cases where fractures are formed from themodified region 7 acting as a start point, and the fractures andmodified region 7 may be exposed at outer surfaces (the front face, rearface, and outer peripheral face) of the object 1.

Here, the laser light L is absorbed in particular in the vicinity of theconverging point within the object 1 while being transmittedtherethrough, whereby the modified region 7 is formed in the object 1(i.e., internal absorption type laser processing). In the case offorming a removing part such as a hole or groove by melting it away fromthe front face 3 (surface absorption type laser processing), theprocessing region gradually progresses from the front face 3 side to therear face side in general.

The modified region 7 in accordance with this embodiment means regionswhose physical characteristics such as density, refractive index, andmechanical strength have attained states different from those of theirsurroundings. Examples of the modified region 7 include molten processedregions, crack regions, dielectric breakdown regions, refractive indexchanged regions, and their mixed regions. Further examples of themodified region 7 include an area where the density has changed fromthat of an unmodified region in a material of the object 1 and an areaformed with a lattice defect (which may collectively be referred to as ahigh-density transitional region).

The molten processed regions, refractive index changed regions, areaswhere the modified region 7 has a density different from that of theunmodified region, or areas formed with a lattice defect may furtherincorporate a fracture (cut or microcrack) therewithin or at aninterface between the modified region 7 and an unmodified region. Theincorporated fracture may be formed over the whole surface of themodified region 7 or in only a part or a plurality of parts thereof.Examples of the object 1 include those containing or constituted bysilicon.

Here, this embodiment forms the modified region 7 in the object 1 andthen etches the object 1, so as to advance the etching selectively alongthe modified region 7 (i.e., along the modified region 7, fracturesincluded in the modified region 7, or fractures from the modified region7), thereby removing a part extending along the modified region 7 in theobject 1. These fractures are also known as cracks, microcracks,fractures, and the like (hereinafter simply referred to as “fractures”).

In the etching in this embodiment, for example, a capillary action orthe like is utilized so that fractures included in the modified region 7of the object 1 or fractures from the modified region 7 are impregnatedwith an etchant, so as to advance (develop) the etching along fracturesurfaces. This advances the etching selectively at a higher etching rate(etching speed) along the fractures in the object 1 and removes them. Atthe same time, by utilizing the characteristic feature that the etchingrate of the modified region 7 itself is high, the etching is selectivelyadvanced along the modified region 7, so as to remove it.

Examples of the etching include a case where the object 1 is immersed inthe etchant (dipping) and a case where the object 1 is coated with theetchant while being rotated (spin etching).

Examples of the etchant include KOH (potassium hydroxide), TMAH (aqueoustetramethylamnionium hydroxide solution), EDP (ethylenediaminepyrocatechol), NaOH (sodium hydroxide), CsOH (cesium hydroxide), NH₄OH(ammonium hydroxide), and hydrazine. The etchant to be used is notlimited to liquids but may be in the form of a gel (jelly or semisolid).Here, the etchant is used at a temperature ranging from ambienttemperature to about 100° C., which is set appropriately according to arequired etching rate or the like. When etching Si with KOH, forexample, the temperature is preferably about 60° C.

As the etching, this embodiment performs anisotropic etching which isetching having a higher (or lower) etching rate in a specific direction.The anisotropic etching is applicable not only to relatively thinobjects but also to thick ones (having a thickness of 800 μm to 100 μm,for example). In this case, even when the surface to be formed with themodified region 7 differs from its plane direction, the etching can beadvanced along the modified region 7. That is, the anisotropic etchinghere enables not only the etching of the plane direction in conformityto the crystal orientation, but also the etching independent of thecrystal orientation.

The interposer manufacturing method in accordance with an embodimentwill now be explained in detail. FIG. 7 is a schematic sectional viewillustrating the interposer manufactured by this embodiment, while FIG.8 is a schematic perspective view of the interposer of FIG. 7. Themanufacturing method of this embodiment manufactures an interposer as arelay board for electrically connecting electronic components to eachother.

As illustrated in FIGS. 7 and 8, an interposer 10 is a siliconinterposer comprising a substrate 10 x and a plurality of through-holeelectrodes 10 y provided in the substrate 10 x. As illustrated in FIG.7, this interposer 10 constitutes connection wiring between asemiconductor device 11 such as an IC chip and a flexible cable(flexible printed board) 12, while converting their wiring pitches.

The substrate 10 x is made of silicon and formed like a flat sheethaving a target thickness M which is 200 μm, for example. Thethrough-hole electrodes 10 y, each including a conductor 13 and pads 14,electrically connect the front and rear sides of the substrate 10 x toeach other. As illustrated in FIG. 8, a plurality of through-holeelectrodes 10 y are arranged in a staggered manner as seen from thefront face of the substrate 10 x. That is, the plurality of through-holeelectrodes 10 y are arranged such that a pair of through-hole electrodes10 y close to each other in the Y direction are shifted from each otherby a half pitch, for example, in the X direction.

FIGS. 9 to 12 are flow diagrams illustrating the interposermanufacturing method in accordance with this embodiment. As illustratedin FIGS. 9 to 12, this embodiment converges the laser light L at theobject 1, so as to form modified regions 7 within the object 1. Then,predetermined parts on the front face 3 side and rear face 21 side ofthe object 1 are removed as removing parts 1 p by anisotropic etching,so as to thin the object 1 to the target thickness M. At the same time,the etching is selectively advanced along the modified regions 7, so asto form a plurality of through holes 24.

As illustrated in FIG. 9( a), the object 1 is a sheet-like siliconsubstrate which is transparent to the wavelength (e.g., 1064 nm) of thelaser light L with which it is irradiated. The object 1 has a thicknessof 300 μm, for example, which is greater than the target thickness M.The object 1 has the front face 3 and rear face 21 (main faces), whichare (100) planes. In the object 1, parts 5 are programmably set as beingspecified by three-dimensional coordinates. The parts 5 have first partto form a modified region 5 x and second part to form a modified region5 y.

The first parts 5 x are set along the parts corresponding to the throughholes 24 (see FIG. 12( c)) within the object 1. The first parts 5 xherein include first part 5 x ₁ extending in the thickness direction ofthe object 1, first part 5 x ₂ tilted with respect to the thicknessdirection, and first part 5 x ₃ tilted with respect to the thicknessdirection by a greater angle than the first part 5 x ₂. The first part 5x ₂, 5 x ₃ extend along (111) planes of the object 1.

The second parts 5 y are set in the removing parts 1 p on the front face3 side and rear face 21 side within the object 1. A plurality of secondparts 5 y are set so as to join with both ends of the first part 5 x,respectively, and extend parallel to the thickness direction of theobject 1.

The following explanations will assume the thickness direction of theobject 1 (irradiation direction of the laser light L) to be the Zdirection, the direction in which the parts 5 (through holes 24) aretilted with respect to the thickness direction to be the X direction,and the direction orthogonal to the X and Y directions to be the Ydirection.

First, when processing the object 1 in this embodiment, the object 1 ismounted on the mount table with the front face 3 facing up.Subsequently, as illustrated in FIG. 9( b), a converging point of thelaser light L (hereinafter simply referred to as “converging point”) islocated at the removing part 1 p on the rear face 21 side within theobject 1. Then, while relatively moving the converging point in the Xdirection, irradiation with the laser light L (hereinafter simplyreferred to as “scan”) is performed in an on/off manner from the frontface 3 side such that modified regions 7 are formed in the parts 5. Thisforms the modified regions 7 at respective positions on the second parts5 y in the removing part 1 p on the rear face 21 side.

Here, since spot irradiation is performed with a pulsed laser light asthe laser light L, the modified regions 7 formed thereby are constitutedby modified spots. Thus formed modified regions 7 include fracturesgenerated from the modified regions 7 (ditto in the following modifiedregions 7).

Next, as illustrated in FIG. 10( a), the position of the convergingpoint in the Z direction is moved by a predetermined amount toward thefront face 3, and then the above-mentioned scan is performed again,whereby modified regions 7 joining on the front face 3 side with theexisting modified regions 7 are newly formed at respective positions onthe second parts 5 y in the removing part 1 p on the rear face 21 side.As a result, modified regions 71 extending parallel to the Z direction(i.e., extending substantially linearly along the Z direction so as notto intersect the Z direction) are formed within the removing part 1 p onthe rear face 21 side.

Next, as illustrated in FIGS. 10( b) to 11(b), the above-mentioned scanis repeatedly performed while progressively changing the position of theconverging point in the Z direction from the rear face 21 side to thefront face 3 side. This forms modified regions 72 joining with theexisting modified regions 71 in the parts corresponding to the throughholes 24 within the object 1, and modified regions 73 joining with theexisting modified regions 72 and extending parallel to the Z direction(i.e., extending substantially linearly along the Z direction so as notto intersect the Z direction) within the removing part 1 p on the frontface 3 side. That is, the modified regions 72 as the first modifiedregions extending in conformity to the through holes 24 are formed inthe parts other than the removing parts 1 p within the object 1, whilethe modified regions 71, 73 as the second modified regions joining withthe respective end parts of the modified regions 72 and extendingstraight in the Z direction are formed in the removing parts 1 p so asnot to be exposed to the front face 3 and rear face 21.

Subsequently, the steps illustrated in FIGS. 9( a) to 11(b) mentionedabove are repeatedly performed while changing the position of theconverging point of the laser light L in the Y direction. The foregoingforms a plurality of modified regions 72 in conformity to a plurality ofthrough holes 24 within the object 1, and a plurality of modifiedregions 71, 73 joining with their corresponding modified regions 72 andextending parallel to the Z direction within the removing parts 1 p.

The modified regions 72 are formed along the first parts 5 x ₁ to 5 x ₃and thus include modified regions 72 ₁ extending in the Z direction,modified regions 72 ₂ tilted in the X direction with respect to the Zdirection, and modified regions 72 ₂ tilted in the same direction by agreater angle than the modified regions 72 ₃. Here, the sizes, lengths,and the like of the modified regions 71, 73 are made such that theetching time required for thinning the object 1 to the target thicknessM and the total of the respective etching times for etching the modifiedregions 71 to 73 equal each other in anisotropic etching in a laterstage.

Next, the object 1 is etched for 60 min with KOH at 85° C., for example,as an etchant. This gradually removes the removing parts 1 p in theobject 1 from the front face 3 side and rear face 21 side, therebyprogressively thinning the object 1. Then, when the object 1 is thinneduntil the modified regions 71, 73 are exposed as illustrated in FIG. 12(a), the modified regions 71, 73 are impregnated with the etchant,whereby etching starts along the modified regions 71, 73. Subsequently,while the object 1 is thinned, its inside is selectively etched awayalong the modified regions 71, 73.

Then, as illustrated in FIG. 12( b), while the removal of the removingparts 1 p advances, so that the object 1 is continuously thinned, theetchant infiltrates from the modified regions 71, 73 into the modifiedregions 72, whereby the etching starts to progress along the modifiedregions 72. Subsequently, while the object 1 is thinned, the inside ofthe object 1 is selectively etched away along the modified regions 72.

Thereafter, while the removal of the removing parts 1 p progresses so asto thin the object 1 further continuously, the etching advances in themodified regions 72. Then, when the thickness of the object 1 becomesthe target thickness M as illustrated in FIG. 12( c), the object 1 ispenetrated along the modified regions 72, whereby the forming of aplurality of through holes 24 completes.

The plurality of through holes 24 are arranged so as to correspond tothe above-mentioned through-hole electrodes 10 y. Specifically, theplurality of through holes 24 are arranged in a staggered manner as seenfrom the front face 3 of the object 1. That is, in the plurality ofthrough holes 24, the through holes 24 aligning in the X direction,which is their tilted direction, are staggered in the Y directionperpendicular to the tilted direction as seen from the front face 3. Inother words, when seen from the front face 3, a group of through holes24 arranged in the X direction align in the Y direction while shiftingin the X direction. Hence, when seen from the front face 3, they arearranged such that one through hole 24 is surrounded by four throughholes 24 which are located close to each other. Here, the plurality ofthrough holes 24 are arranged such that a pair of through holes 24, 24close to each other in the Y direction shift from each other by a halfpitch in the X direction, for example.

Since the anisotropic etching is performed as mentioned above in thisembodiment, the (111) planes of the object 1 are harder to etch (have alower etching rate). Therefore, in the modified regions 72 extendingalong the (111) planes, the etching advances favorably, so that theinner faces of the resulting through holes 24 become smooth surfaceswith less depressions and projections. As illustrated in FIG. 13, thethrough holes 24 have substantially rectangular (diamond-shaped) crosssections, while varying less in inner sizes along their axes.

As illustrated in FIG. 12( c), the through holes 24 are formed along themodified regions 72 ₁ to 72 ₂, respectively, and thus include throughholes 24 ₁ extending in the Z direction, through holes 24 ₂ tilted inthe X direction with respect to the Z direction, and through holes 24 ₃tilted in the same direction by a greater angle than the through holes24 ₂.

Next, the object 1 is oxidized by wet oxidation or the like, so as toproduce an electrically insulating oxide film on the inner face (innerwall) of each through hole 24. Here, as illustrated in FIG. 13, theinner face of the through hole 24 is a smooth surface, while its crosssection is substantially rectangular, so that projections where theinsulating film is hard to grow do not exist on the inner face of thethrough hole 24, whereby a uniform insulating film 15 can be formed, soas to suppress defects in the insulating film 15.

Thereafter, a conductor 13 is inserted into each through hole 24, andpads 14 are formed on the front face 3 and rear face 21 so as toelectrically connect with the conductor 13. This constructs the object 1as the substrate 10 x and the through holes 24 as the through-holeelectrodes 10 y, thereby yielding the interposer 10.

As in the foregoing, the through holes 24 aligning in the X directionare staggered in the Y direction when seen from the front face 3 of theobject 1 in this embodiment. Therefore, a plurality of through holes 24and, as a consequence, a plurality of through-hole electrodes 10 y canbe arranged denser than in the case where the plurality of through holesare arranged into a simple lattice as seen from the front face 3, forexample, whereby the resulting interposer 10 can be made smaller. Thiscan also increase the numbers of through holes 24 and through-holeelectrodes 10 y that can be formed in the object 1, thereby achieving ahigher wiring density in the interposer 10.

As mentioned above, since the through hole 24 can be formed with arectangular cross section, the insulating film 15 can be made uniform,so as to suppress defects in the insulating film 15, thereby securingelectric conduction in the through-hole electrode 10 y and preventingconnections from failing, thus attaining high reliability.

In this embodiment, as mentioned above, the etching for the modifiedregions 72 does not begin to progress when the object 1 is at the targetthickness, but is induced to start to advance by the modified regions71, 73 formed in the removing parts 1 p when thinning the object 1 tothe target thickness M by anisotropic etching, and the forming of thethrough holes 24 completes when the object 1 is thinned to the targetthickness M. This can inhibit the opening sides (front face 3 side andrear face 21 side) of the through holes 24 from being removed in excessand increasing their aperture sizes (opening sizes) on the opening sidesand inner widths, whereby the through holes 24 can be formed accuratelyin the object 1 having the target thickness M.

That is, in a method for manufacturing the interposer 10 by masklesslaser processing, this embodiment can form desirable through holes 24while adjusting the thickness of the object 1. Specifically, themodified regions 71, 73 for guiding the etching to the modified regions72 (regulating the etching of the modified regions 72) are formed in theremoving parts 1 p, whereby the forming of the through holes 24 can becompleted at the time of thinning to the target thickness M inanisotropic etching in a later stage. Therefore, the thickness of theobject 1 and the aperture size of the through holes 24 can be controlledaccurately at the same time, so that appropriately forming the modifiedregions 71, 73, for example, can adjust the time required forpenetrating the modified regions 72, whereby the final thickness of thesubstrate 10 x can be set.

Since the modified regions 71, 73 extend parallel to the Z direction asmentioned above, it becomes easier to specify and manage the convergingpoint of the laser light L when forming the modified regions 71, 73,whereby the laser processing can be facilitated.

FIG. 14( a) is an enlarged sectional view illustrating a part of theobject after forming modified regions therein, while FIG. 14( b) is anenlarged sectional view illustrating a part of the object after formingthrough holes therein. As illustrated in FIG. 14, when the modifiedregions 73 extending parallel to the Z direction are formed in theremoving part p1 such as to join with the modified regions 72 ₂ (i.e.,when the modified regions 73 are stacked along a line parallel to the Zdirection), the aperture size H on the opening side of the through hole24 ₂ formed by anisotropic etching is relatively small in conformity tothe size of the modified regions 73.

When modified regions 73′ tilted in the Z direction are formed such asto join with the modified regions 72 ₂ (i.e., when the modified regions73′ are formed by stacking while being shifted in the X direction so asto be tilted with respect to the Z direction), on the other hand, theaperture size H′ on the opening side of the resulting through hole 24 ₂′is larger than the aperture size H. Therefore, when reducing theaperture size H on the opening side of the through hole 24, it ispreferred for the modified regions 73 (71) formed in the removing part 1p to extend parallel to the Z direction.

Since the modified regions 71, 73 are not exposed to the front face 3and rear face 21 of the object 1 as mentioned above, this embodiment caninhibit the etching of the modified regions 72 from advancing in excesswhen the object 1 attains the target thickness M and thereby increasingthe aperture size on the opening side of the through hole 24 and itsinner width.

As mentioned above, this embodiment repeatedly performs the scan alongthe X direction while changing the depth position of the convergingpoint in the Z direction (see FIGS. 9( b) to 11(b); first step) andrepeatedly performs the same while changing the position of theconverging point in the Y direction (second step), thereby forming aplurality of through holes 24. This can restrain the converging pointfrom moving uselessly and enables rapid processing, thereby shorteningthe takt time (processing time) and lowering the cost.

The interposer 10 in accordance with this embodiment has thethrough-hole electrodes 10 y tilted with respect to the Z direction,which makes it unnecessary to stack a plurality of substrates 10 x forchanging wiring pitches, whereby its weight, thickness, and cost can bereduced. In addition, this can simplify the wiring and attain very finewiring pitches, so as to facilitate designing and lower the electricresistance in wiring.

Since the substrate 10 x is made of silicon, this embodiment can enhanceheat dissipation while restraining the wiring from breaking under theinfluence of thermal expansion differences when the semiconductor device11 is made of silicon.

When forming the through holes 24, this embodiment can remove themodified regions 7 and fractures incorporated therein from the object 1after the processing by anisotropic etching and thus can improve itsstrength and quality. Since no cutting dusts occur during processing, anenvironment-friendly processing method can be achieved.

Though a preferred embodiment of the present invention has beenexplained in the foregoing, the present invention is not limited theretobut may be modified or applied to others within the scope not changingthe gist recited in each claim.

For example, the laser light entrance surface for forming the modifiedregions 7 is not limited to the front face 3 of the object 1, but may bethe rear face 21 of the object 1. Though the modified regions 71, 73respectively joining with the modified regions 72 on the rear face 21side and the front face 3 side are formed in the removing parts 1 p asthose guiding the etching to the modified regions 72 in theabove-mentioned embodiment, one of them may be formed alone.

Though the modified regions 71, 73 extending parallel to the Z directionare formed such as to join with the respective end parts of the modifiedregions 72 in the above-mentioned embodiment, the modified regions 71,73 are not limited to those extending parallel to the Z direction, butmay extend along the modified regions 72, for example. Theabove-mentioned term “parallel” encompasses those substantially paralleland those intended to become parallel.

The direction and order of scans in the above-mentioned embodiment arenot limited. For example, the scan along the X direction may berepeatedly performed while changing the position of the converging pointin the Y direction, and the same may be repeatedly performed whilechanging the depth position of the converging point in the Z direction,so as to form a plurality of through holes 24. For example, irradiationwith the laser light L may be performed while moving its convergingpoint along one through hole 24 so as to form a modified region 7, andthe same may be repeated by the number of through holes 24, so as toform a plurality of through holes 24.

The on/off irradiation with the laser light L in the above-mentionedembodiment may be performed not only by controlling the on/off of theemission of the laser light L, but also by opening/closing a shutterdisposed on the optical path of the laser light L or by masking on/offthe front face 3 of the object 1, for example. Further, the intensity ofthe laser light L may be controlled between an intensity at a thresholdfor forming the modified regions 7 (processing threshold) or higher andan intensity lower than the processing threshold.

The above-mentioned embodiment can adjust the etchant (e.g., addadditives such as alcohols and surfactants), so as to change the etchantrate in a specific crystal orientation, thereby forming a through holehaving a desirable rectangular cross-sectional form (inner wall form).For example, anisotropic etching with an etchant doped with IPA(isopropyl alcohol) can make a through hole 24 with an oblong crosssection as illustrated in FIG. 15( a). For example, anisotropic etchingwith an etchant doped with a surfactant can make a through hole 24 witha square cross section as illustrated in FIG. 15( b).

Though the interposer 10 convert wiring pitches and pitches of theplurality of through-hole electrodes 10 y on the front face is differentfrom ones on the rear face in the above-mentioned embodiment, theabove-mentioned embodiment can manufacture a interposer 50 asillustrated in FIG. 16.

In the interposer 50, pitches of the plurality of through-holeelectrodes 10 y on the front face and ones on the rear face equal eachother, arrangement pattern of through-hole electrodes 10 y on the frontface and on the rear face equal each other. That is, the plurality ofthrough-hole electrodes 10 y are arranged in a staggered manner on thefront face and on the rear face as seen in the Z direction. Here,horizontal position of the through-hole electrodes 10 y are differenteach other between on the front face and on the rear face of thesubstrate 10. That is to say, the through-hole electrodes 10 y areprovided so as to arrange the same pattern and shift in the X directionor/and Y direction between on the front face and on the rear face.

INDUSTRIAL APPLICABILITY

The present invention can provide a method for manufacturing aninterposer which can be made smaller while securing high reliability.

REFERENCE SIGNS LIST

1 . . . object; 1 p . . . removing part (part to be removed); 3 . . .front face (main face); 7 . . . modified region; 10, 50 . . .interposer; 10 y . . . through-hole electrode; 15 . . . insulating film;21 . . . rear face (main face); 24 . . . through hole; 71, 73 . . .modified region (second modified region); 72 . . . modified region(first modified region); L . . . laser light; M . . . target thickness

The invention claimed is:
 1. A method for manufacturing an interposerequipped with a plurality of through-hole electrodes, the methodcomprising: a laser light converging step of converging a laser light ata sheet-like object to be processed made of silicon so as to form amodified region in the object; an etching step of anisotropicallyetching the object after the laser light converging step so as toadvance etching selectively along the modified region and form aplurality of through holes in the object, each through hole having arectangular cross section; an insulating film forming step of forming aninsulating film on an inner wall of each through hole after the etchingstep; and a through-hole electrode forming step of inserting a conductorinto the through holes so as to form the through-hole electrodes afterthe insulating film forming step; wherein the plurality of through holesare aligned in rows, each through hole of one row having a differenttilt angle with respect to a neighboring hole in the one row, andneighboring rows being arranged so that the through holes of therespective rows are staggered towards each other.
 2. A method formanufacturing an interposer according to claim 1, wherein the laserlight converging step forms a first modified region as the modifiedregion in a part corresponding to the through hole in the object and asecond modified region as the modified region joining with the firstmodified region in a part to be removed upon thinning by the anisotropicetching; and wherein the etching step advances the etching selectivelyalong the second modified region and then along the first modifiedregion while thinning the object to a target thickness and completesforming the through holes when the object is at the target thickness. 3.A method for manufacturing an interposer according to claim 2, whereinthe second modified region extends parallel to the thickness directionof the object.
 4. A method for manufacturing an interposer according toclaim 3, wherein the object has a main face which is a (100) plane.
 5. Amethod for manufacturing an interposer according to claim 4, wherein thelaser light converging step comprises: a first step of repeatedlyperforming a step of irradiating the object with the laser light whilerelatively moving a converging point of the laser light along a firstdirection orthogonal to a laser light irradiation direction, whilechanging a depth position of the converging point in the irradiationdirection; and a second step of repeatedly performing the first stepwhile changing a position of the converging point in a second directionorthogonal to the irradiation direction and first direction.
 6. A methodfor manufacturing an interposer according to claim 3, wherein the laserlight converging step comprises: a first step of repeatedly performing astep of irradiating the object with the laser light while relativelymoving a converging point of the laser light along a first directionorthogonal to a laser light irradiation direction, while changing adepth position of the converging point in the irradiation direction; anda second step of repeatedly performing the first step while changing aposition of the converging point in a second direction orthogonal to theirradiation direction and first direction.
 7. A method for manufacturingan interposer according to claim 2, wherein the object has a main facewhich is a (100) plane.
 8. A method for manufacturing an interposeraccording to claim 7, wherein the laser light converging step comprises:a first step of repeatedly performing a step of irradiating the objectwith the laser light while relatively moving a converging point of thelaser light along a first direction orthogonal to a laser lightirradiation direction, while changing a depth position of the convergingpoint in the irradiation direction; and a second step of repeatedlyperforming the first step while changing a position of the convergingpoint in a second direction orthogonal to the irradiation direction andfirst direction.
 9. A method for manufacturing an interposer accordingto claim 2, wherein the laser light converging step comprises: a firststep of repeatedly performing a step of irradiating the object with thelaser light while relatively moving a converging point of the laserlight along a first direction orthogonal to a laser light irradiationdirection, while changing a depth position of the converging point inthe irradiation direction; and a second step of repeatedly performingthe first step while changing a position of the converging point in asecond direction orthogonal to the irradiation direction and firstdirection.
 10. A method for manufacturing an interposer according toclaim 1, wherein the second modified region extends parallel to thethickness direction of the object.
 11. A method for manufacturing aninterposer according to claim 10, wherein the object has a main facewhich is a (100) plane.
 12. A method for manufacturing an interposeraccording to claim 11, wherein the laser light converging stepcomprises: a first step of repeatedly performing a step of irradiatingthe object with the laser light while relatively moving a convergingpoint of the laser light along a first direction orthogonal to a laserlight irradiation direction, while changing a depth position of theconverging point in the irradiation direction; and a second step ofrepeatedly performing the first step while changing a position of theconverging point in a second direction orthogonal to the irradiationdirection and first direction.
 13. A method for manufacturing aninterposer according to claim 10, wherein the laser light convergingstep comprises: a first step of repeatedly performing a step ofirradiating the object with the laser light while relatively moving aconverging point of the laser light along a first direction orthogonalto a laser light irradiation direction, while changing a depth positionof the converging point in the irradiation direction; and a second stepof repeatedly performing the first step while changing a position of theconverging point in a second direction orthogonal to the irradiationdirection and first direction.
 14. A method for manufacturing aninterposer according to claim 1, wherein the object has a main facewhich is a (100) plane.
 15. A method for manufacturing an interposeraccording to claim 14, wherein the laser light converging stepcomprises: a first step of repeatedly performing a step of irradiatingthe object with the laser light while relatively moving a convergingpoint of the laser light along a first direction orthogonal to a laserlight irradiation direction, while changing a depth position of theconverging point in the irradiation direction; and a second step ofrepeatedly performing the first step while changing a position of theconverging point in a second direction orthogonal to the irradiationdirection and first direction.
 16. A method for manufacturing aninterposer according to claim 1, wherein the laser light converging stepcomprises: a first step of repeatedly performing a step of irradiatingthe object with the laser light while relatively moving a convergingpoint of the laser light along a first direction orthogonal to a laserlight irradiation direction, while changing a depth position of theconverging point in the irradiation direction; and a second step ofrepeatedly performing the first step while changing a position of theconverging point in a second direction orthogonal to the irradiationdirection and first direction.